This invention relates generally to fuel-burning heaters having combustion chambers and relates, more particularly, to an afterburner for use at the discharge end of the combustion chamber of such a heater.
The type of heater with which this invention is concerned includes a combustion chamber within which the combustion of fuel, such as oil, takes place. The fuel is introduced into the combustion chamber where it is mixed with air and ignited at the inlet end of the chamber, and the resulting products of combustion flow toward and out of the opposite, or discharge, end of the chamber.
Incomplete combustion is not uncommon in heaters of this type due, for example, to the development of droplets of fuel within the combustion chamber which are not uniform in size or to an uneven mixing of the fuel with air prior to combustion. To reduce the likelihood that unburned fuel droplets (e.g., hydrocarbons) escape the heater with the products of combustion, the heater may be provided with an afterburner positioned within the discharge end of the combustion chamber.
The afterburner commonly includes a nose cone portion and a ring portion arranged substantially in the center of the discharge end of the combustion chamber. The nose cone portion is commonly joined to the ring portion with struts which maintain the nose cone portion and ring portion in spaced relationship to provide a passage through which combustion products must exit the heater. During operation of a heater within which an afterburner is positioned, the flow of the products of combustion from the combustion chamber is altered by the nose cone portion so that unburned fuel droplets are forced to contact the afterburner. Since the afterburner normally possesses a relatively high temperature during heater operation due to its exposure and proximity to the combustion reaction, the contact between the unburned fuel droplets and the surface of the afterburner and the exposure to air in the exhaust gases normally completes the combustion process.
Heretofore, afterburners have been constructed with a nose cone portion and a ring portion which are separate pieces. In particular, the ring portion is formed as one piece and the nose cone portion is formed as a second piece separate from that of the ring portion piece. The ring portion and nose cone portion are thereafter attached together with, for example, struts to provide the desired spaced relationship between the ring portion and the nose cone portion. It would be desirable to provide an afterburner which is constructed as a unit out of a single piece of material in order to circumvent costs (e.g., material and labor costs) ordinarily involved in constructing an afterburner of two-piece construction.
Accordingly, it is an object of the present invention to provide a new and improved afterburner for a heater of the aforedescribed class which is constructed as a unit out of a single piece of material and a method of constructing the afterburner.
Another object of the present invention is to provide such an afterburner whose construction reduces the likelihood of warpage or damage to the afterburner or other components of the heater due to thermal expansion and contraction due to heater operation.
Still another object of the present invention is to provide such an afterburner which limits the introduction of direct light into the combustion chamber through the discharge end thereof wherein such indirect light may otherwise result in a false reading by a photocell positioned rearward of the combustion chamber for monitoring the flame within the combustion chamber.
A further object of the present invention is to provide such an afterburner which is economical to construct and effective in operation.